Abstract: Some of the first results are reported from RISE - a new fast camera mountedon the Liverpool Telescope primarily designed to obtain high time resolutionlight curves of transiting extrasolar planets for the purpose of transittiming. A full and partial transit of WASP-3 are presented, and a Monte CarloMarkov Chain analysis is used to update the parameters from the discoverypaper. This results in a planetary radius of 1.29^{+0.05} {-0.12} R J andtherefore a density of 0.82^{+0.14} {-0.09} p J, consistent with previousresults. The inclination is 85.07^{+0.15} {-0.16} deg, in agreement but with asignificant improvement in the precision with the previously determined value.Central transit times are found to be consistent with the ephemeris given inthe discovery paper. However, a new ephemeris calculated using the longerbaseline results in T c0 = 2454605.55915 +- 0.00023 HJD and P = 1.846835 +-0.000002 days.